Optical birefringence measurements of antiferromagnets with Ising spin chains

Abstract

Optical birefringence measurements were performed on Ising-spin antiferromagnets with the chemical formula ACo[Formula: see text]. The temperature dependences of the birefringences of CsCoCl3 and CsCoBr3 reflect the thermal shrinkage of the crystal lattice and the development of magnetic short-range correlation in Ising spin chains. Moreover, the temperature dependences of the birefringences of RbCoBr3 and TlCoCl3 show marked anomalies at structural phase transition points. We demonstrate a method of numerically analyzing the birefringence in magnetic compounds that undergo structural phase transitions.